1. Field of the Invention
The present invention relates to a movable contact assembly for a circuit breaker, and more particularly, to a movable contact assembly for a circuit breaker in which a pressurizing protrusion for pushing a catch is provided at each of movable contact fingers and thus, when current limiting interruption occurs in any one of the movable contact fingers, reinputting of the movable contact fingers is prevented such that blocking thereof is stably kept.
2. Discussion of Related Art
Generally, circuit breakers are electrical devices which are installed at a power transmission site, a power substation, or an electrical circuit to cut off a circuit when a load is opened or closed, the ground is performed, or an accident such as a short circuit or the like occurs. An air circuit breaker among such circuit breakers is a circuit breaker which uses air as an extinguishing medium and is mainly employed for a low voltage device, and a movable contact assembly of a circuit breaker according to the present invention may be applied to the air circuit breaker and the like.
Interruption types of circuit breakers includes delay trip (demonstration trip) interruption for preventing overheating when an overcurrent flows (e.g., 1 to 1.5 times a rated current), and instantaneous trip interruption when a fault current (e.g., several to 10 times the rated current) occurs. The instantaneous trip interruption includes interruption caused by the mechanical action of an over current relay or a switching mechanism (instantaneous interruption in a general sense), and current limiting interruption caused by an electromagnetic repulsive force between a fixed contact and a movable contact.
The current limiting interruption is performed to immediately separate the movable contact from the fixed contact using the electromagnetic repulsive force generated between the movable contact and the fixed contact when a large current such as a short-circuit current flows, thereby cutting off a circuit to protect the circuit and a load, and a circuit breaker employing the current limiting interruption may be referred to as a current limiting circuit breaker.
FIG. 1 is an exploded perspective view of a movable contact assembly of a circuit breaker according to a related art. This related art refers to Korean Registered Patent No. 10-1079012 entitled “Current Limiting Circuit Breaker for Electric Wiring.” A mover (movable contact) assembly 100 of a circuit breaker for electric wiring includes a terminal 180 formed of a conductive material and installed inside the circuit breaker, a connector 170 protruding from one side of the terminal 180, a movable contact 110 assembled to the connector 170 through a pin 200 and provided to be pivoted relative to the connector 170 at a predetermined angle, a side holder 120 provided at both sides of the movable contact 110, assembled to the connector 170 through the pin 200, and configured to adjust a position of the movable contact 110, a movable contact holder 125 coupled above the side holder 120 and configured to support a guide 115 of the movable contact 110, a link 126 and a link pin 127 which are installed at the movable contact holder 125 and configured to transmit power of a switching mechanism, a spring holder 130 fixed to the side holder 120 and configured to accommodate an upper portion of a spring 140 and apply a constant load when the movable contact 110 is pivoted, a latch 150 assembled to the side holder 120 and configured to be pivoted within a predetermined section, a roller 155 pivotably coupled to the latch 150, and a catch 160 pivotably installed at the terminal 180 and configured to restrict pivoting of the movable contact 110.
Here, the catch 160 is provided to prevent a phenomenon (rebound phenomenon) in which the movable contact 110 returns by colliding with a case or base mold (not shown) after being separated from a stator due to current limiting interruption. That is, the catch 160 prevents a reinputting of the movable contact 110 into the stator 210 during the current limiting interruption. When interruption by the mechanical action of the switching mechanism is performed, the movable contact holder 125 is moved together with the movable contact 110 such that a phenomenon in which the movable contact 110 rebounds independently may not occur, but when current limiting interruption is performed, the movable contact 110 is separated from the movable contact holder 125 and is moved independently such that there is a probability in which the movable contact 110 is input again due to a rebound phenomenon and thus the catch 160 is provided to prevent the reinputting of the movable contact 110.
In the related art, however, the action of the catch 160 becomes operable only when all movable contacts 110 (two movable contacts in FIG. 1) are moved together therewith. The aforementioned will be described in detail with reference to FIG. 2.
Two movable contacts 110 will be distinguished and referred to as a first movable contact 111 and a second movable contact 112. Catch recesses 111a and 112a are respectively formed at lower portions of the first movable contact 111 and the second movable contact 112.
When both the first movable contact 111 and the second movable contact 112 are separated from the stator 210 due to current limiting interruption, the catch recesses 111a and 112a are moved upward to a position at which a protruding contact part is formed on an upper surface of the catch 160 (to a position of the first movable contact 111 in FIG. 2). Since the catch 160 receives a counterclockwise force due to the action of a torsion spring 165, the catch 160 is inserted into the catch recesses 111a and 112a of the first movable contact 111 and the second movable contact 112 to restrict clockwise pivots of the first movable contact 111 and the second movable contact 112, such that the reinputting of the first movable contact 111 and the second movable contact 112 are prevented.
As shown in FIG. 2, however, when the second movable contact 112 is kept in the input state and only the first movable contact 111 is opened, that is, when any one of the first movable contact 111 and the second movable contact 112 is not opened, the catch 160 interferes with a non-opened movable contact (the second movable contact 112 in FIG. 2) and thus is prevented from being input into the catch recesses 111a and 112a such that an effect of preventing a reinputting cannot be achieved.